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Biomedical subjects

Y Gao

Publications and source records attributed to Y Gao.

At least 397 records · Page 22Linked to original sources
PubMed1995

Effectiveness of Norplant implants through seven years: a large-scale study in China.

The effectiveness of Norplant implants over a seven year period of continuous use was studied in a multicenter trial. Pregnancy rates were 0.4 per 100 in both year six and year seven. More than 3,600 women completed 6 years and more than 2,400 women completed 7 years. Pregnancy rates increased with weight (p < .05) and decreased with age, but in years 6 and 7 combined, the pregnancy rate neither reached nor exceeded 1 per 100 woman years in any 5 year age group or in any 10 kg weight group.

Adult↗
PubMed1995

The maize mitochondrial genome: dynamic, yet functional.

The organization of the mitochondrial genome of higher plants is complex. It has two striking features: a large size that can vary among plant species; and the ability to undergo homologous recombination that results in variation within species. From cosmid clone mapping studies, the total genetic information of the plant mitochondrial genome can be arranged into a single circular molecule that is referred to as the master chromosome. This circular DNA molecule contains repeated sequences that can generate, via intramolecular recombination, either isomeric forms of the master chromosome or smaller subgenomic circular DNA molecules. The maize mitochondrial genome is the most complex and largest mitochondrial genome for which a physical map is presently available. Its organization varies considerably among the different maize cytotypes. In an attempt to understand the numerous different mitochondrial DNA rearrangements encountered among those cytotypes, we have proposed a general model of genome evolution that can explain a multitude of genomic rearrangements, not only for the maize mitochondrial DNA but also for other higher plant mitochondrial genomes as well.

Biological Evolution↗
PubMed1995

An etoposide-resistant lung cancer subline overexpresses the multidrug resistance-associated protein.

We have characterised an etoposide-resistant subline of the small-cell lung cancer cell line, UMCC-1, derived at our centre. Subline UMCC-1/VP was developed by culturing the parent line in increasing concentrations of etoposide over 16 months. UMCC-1/VP is 20-fold resistant to etoposide by MTT assays, relative to the parent line, and is cross-resistant to doxorubicin, vincristine and actinomycin D, but not to taxol, cisplatin, melphalan, thiotepa or idarubicin. Topoisomerase II immunoblotting demonstrates a 50% reduction of the protein in the resistant subline. The UMCC-1/VP subline demonstrates a marked decrease in the accumulation of [3H]etoposide relative to the parent line, as well as a modest reduction in the accumulation of daunorubicin. Reverse transcription-polymerase chain reaction assays demonstrate no detectable mdr1 expression but marked expression of the multidrug resistance-associated protein (MRP) gene in the resistant subline. Northern blotting with an MRP cDNA probe confirms marked overexpression of the MRP gene only in the UMCC-1/VP subline. Western blotting with antisera against MRP peptide confirms a 195 kDa protein band in the UMCC-1/VP subline. Southern blotting experiments demonstrate a 10-fold amplification of the MRP gene in the resistant subline. Depletion of glutathione with buthionine sulphoximine sensitised UMCC-1/VP cells to daunorubicin and etoposide. Our studies indicate that MRP gene expression may be induced by etoposide and may lead to reduced accumulation of the drug.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1995

Biological degradation of resin acids in wood chips by wood-inhabiting fungi.

Resin acids in many pulp mill effluents are primary sources of toxicity to fish. Inconsistent biological detoxification of chlorinated and nonchlorinated resin acids in secondary treatment of pulp mill effluents is a continuing source of concern. An alternative approach to effluent detoxification is to remove or modify the toxic compounds present in wood chips prior to pulping. Results from experiments in which lodgepole pine sapwood chips were inoculated with several fungal candidates indicate that the total resin acid content can be reduced by up to 67% after fungal growth. Such a treatment could be an efficient and environmentally acceptable way for deresinating wood chips and so decreasing the toxicity of pulp mill effluents.

Biodegradation, Environmental↗
PubMed1995

Cooperative binding of multimeric phosphoprotein (P) of vesicular stomatitis virus to polymerase (L) and template: pathways of assembly.

It was previously shown that the phosphoprotein (P) of vesicular stomatitis virus must undergo phosphorylation-dependent multimerization to become transcriptionally active. Phosphorylation at S-60 and/or T-62 by casein kinase II or substitution of these residues by D is required for multimer formation. We now find that substitution of either one of these residues by A prevents phosphorylation by casein kinase II and multimer formation. The binding of multimeric P to the other two transcriptional components of vesicular stomatitis virus (L protein and the N-RNA template) has been characterized by using P immobilized on beads through its poly(His) tag to facilitate recovery of bound complexes. Multimerization of P was absolutely required for binding to both L and template. Multimeric P combined with the polymerase enzyme (L) in a stoichiometric 1:1 complex, which bound to the N-RNA template much more strongly than multimeric P alone. Substitution of S-227 and S-233 by A residues had no effect on multimerization or binding of L to P but prevented binding of both P and L to template and abolished transcriptional activity. In contrast, substitution of these residues with D residues had no effect on template binding or activity. However, substitution at these sites by either D or A largely abolished phosphorylation by L-associated kinases, thus identifying S-227 and S-233 as the major sites targeted by these kinases and confirming that phosphorylation of P protein by L-associated kinases is without transcriptional effect.

Animals↗
PubMed1995

Vesicle fusion proteins in rat inner medullary collecting duct and amphibian bladder.

The delivery of water channels to the apical membrane in response to antidiuretic hormone (ADH) requires the targeting of channel-containing vesicles to specific sites in the membrane, followed by fusion and exocytosis. A complex array of proteins is now believed to mediate targeting and fusion in eukaryotic cells. They include N-ethylmaleimide-sensitive fusion protein (NSF), soluble NSF attachment proteins (SNAP), and cellubrevin, a vesicle-associated protein present in the nerve terminal. We asked whether these proteins are in epithelial cells of rat inner medullary collecting duct (IMCD) and amphibian bladder. Immunoblots on both tissues showed the presence of NSF and alpha-SNAP. Cellubrevin was present in immunoblots of the IMCD, but not the bladder. Immunogold electron microscopy showed NSF, alpha-SNAP, and cellubrevin in rat IMCD cells, with vesicular labeling. In the bladder, NSF was seen on vesicles and aggrephores. We conclude that components of the vesicle-targeting and fusion systems are present in kidney and amphibian bladder and may mediate a wide variety of fusion events, including those initiated by ADH.

Animals↗
PubMed1995

Heterogeneity in role of endothelium-derived NO in pulmonary arteries and veins of full-term fetal lambs.

Endothelium-derived nitric oxide (EDNO) modulates fetal pulmonary vasoactivity. The role of EDNO in regulation of vasomotor tone in fetal pulmonary arteries vs. that in veins is not known. We have investigated the role of EDNO in the responses of pulmonary arteries and veins of full-term fetal lambs. Fourth-generation pulmonary arterial and venous rings were suspended in organ chambers filled with modified Krebs-Ringer bicarbonate solution (95% O2-5% CO2 at 37 degrees C), and their isometric force was measured. N omega-nitro-L-arginine had no effect on the resting tension of pulmonary arteries with endothelium but caused contraction of pulmonary veins with endothelium. The basal level of intracellular guanosine 3',5'-cyclic monophosphate (cGMP) of pulmonary veins with endothelium was higher than that of arteries with endothelium. In pulmonary arteries, bradykinin, but not acetylcholine, induced endothelium-dependent relaxation and an increase in cGMP content. In pulmonary veins, acetylcholine, but not bradykinin, induced endothelium-dependent relaxation and an increase in cGMP content. Agonist-induced maximal relaxation and increases in cGMP content were smaller in pulmonary arteries than in veins. All these endothelium-dependent responses were abolished by N omega-nitro-L-arginine. In tissues without endothelium, nitric oxide induced significantly less relaxation and less increase in cGMP content in pulmonary arteries than in pulmonary veins. All vessels relaxed similarly to 8-bromoguanosine 3',5'-cyclic monophosphate. Our data suggest that the role of EDNO in modulating tone differs between pulmonary arteries and veins in full-term fetal lambs.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1995

PAF induces relaxation of pulmonary arteries but contraction of pulmonary veins in the ferret.

The present study was designed to determine whether platelet-activating factor (PAF) has different effects on pulmonary arteries and veins. Third-order pulmonary arterial and venous rings of the ferret were suspended in organ chambers filled with modified Krebs-Ringer bicarbonate solution (95% O2-5% CO2, 37 degrees C) and their isometric tension was recorded. Under basal conditions, PAF had no effect on the resting tension of arteries but induced an endothelium-dependent contraction of veins. The contraction was not affected by BW-755C (an inhibitor of cyclooxygenase and lipoxygenase), BQ-123 [an antagonist of endothelin (ET) A (ETA) receptors)], or IRL-1038 (an antagonist of ETB receptors). PAF had no effect on veins during contraction to prostaglandin F2 alpha (PGF 2 alpha) but induced an endothelium-dependent relaxation of arteries. The relaxation was abolished by N omega-nitro-L-arginine. Incubation with PAF for 30 min augmented contractions of veins with endothelium to PGF 2 alpha. The augmentation was not affected by BW-755C, BQ-123, or IRL-1038. Pretreatment with PAF had no effect on the response of veins to phenylephrine or on the response of arteries to either PGF 2 alpha or phenylephrine. These observations demonstrated that, in the ferret, PAF affected differently the response of pulmonary arteries and veins and that the endothelium plays a critical role in the PAF-induced effects. Furthermore, the PAF-induced effects appear not to be mediated by metabolites of arachidonic acid and ET.

Animals↗
PubMed1995

Endothelium-derived nitric oxide plays a larger role in pulmonary veins than in arteries of newborn lambs.

In perinatal lungs, veins contribute substantially to total pulmonary vascular resistance. The present study was designed to determine the role of endothelium-derived nitric oxide (EDNO) in modulating the responsiveness of pulmonary veins and arteries in newborn lambs. Fourth-order pulmonary arterial and venous rings of newborn lambs were suspended in organ chambers filled with modified Krebs-Ringer bicarbonate solution (95% O2/5% CO2, 37 degrees C), and their isometric force was measured. Nitro-L-arginine had no effect on the resting tension of pulmonary arteries but caused an endothelium-dependent contraction of pulmonary veins. During contraction to endothelin-1 or U46619, acetylcholine, bradykinin, and calcium ionophore A23187 induced larger endothelium-dependent relaxation in pulmonary veins than in arteries. The endothelium-dependent relaxation of pulmonary vessels was abolished by nitro-L-arginine. In vessels without endothelium, nitric oxide induced significantly greater relaxation in pulmonary veins than in arteries. All vessels relaxed similarly to 8-bromo-cGMP. Radioimmunoassay showed that the basal level of intracellular cGMP of pulmonary veins with endothelium was higher than that of arteries with endothelium. Acetylcholine, bradykinin, and calcium ionophore A23187 induced a significantly larger endothelium-dependent increase in the intracellular content of cGMP in pulmonary veins than in arteries. In vessels without endothelium, nitric oxide induced a larger increase in cGMP content in pulmonary veins than in arteries. The present study suggests that EDNO may play a larger role in modulation of pulmonary venous than arterial reactivity, which may be mainly due to a difference in the activity of soluble guanylate cyclase in vascular smooth muscle.

Acetylcholine↗
PubMed1995

Reversible intercellular coupling by regulated expression of a gap junction channel gene.

Direct intercellular coupling through gap junction channels has been implicated in diverse processes including cellular differentiation, growth control, metabolic cooperativity and electronic coupling and natural and induced mutations in connexin genes have been described in human and experimental disease states. Genetic systems in which the extent of coupling could be reversibly regulated would provide an important approach for examining these potential functional roles, both in vitro and in vivo. Here we describe the generation and characterization of cell lines in which the extent of coupling is reversibly controlled at the transcriptional level. Plasmids encoding a tetracycline-controlled transactivator and a tetracycline-responsive connexin32 target gene were introduced in the communication-deficient SKHep1 cell line. Quantitative immunoblotting and confocal immunofluorescence microscopy with connexin32-specific antibodies demonstrated that expression of connexin32 in stable transfectants was tightly regulated by tetracycline treatment. Moreover, transfectants exhibited a highly coupled phenotype which was rapidly and reversibly converted to the communication deficient parental state after tetracycline treatment. Time constants for decay of the messenger RNA, protein and functional coupling were similar (approximately 4 hrs), implying that transcription was rate-limiting and that separate long-lived pools of connexin32 protein were absent. In contrast to other approaches in which the extent of coupling is pharmacologically regulated by altering channel gating characteristics or by generalized blockade of transcription or translation, in this system intercellular communication is regulated by directly controlling connexin gene expression.

Carcinoma, Hepatocellular↗
PubMed1995

Overexpression of c-erbB-2 and p21 oncoproteins in human radiation-induced skin ulcers.

We studied the overexpression of c-erbB-2 and p21 oncoproteins in human radiation-induced skin ulcers using immunohistochemistry. We found that the positive rate of overexpression of c-erbB-2 and p21 oncoproteins was 92.0 and 92.9%, respectively. The overexpression of c-erbB-2 oncoprotein was observed mainly in the cell membrane of squamous epithelial cells and in the cytoplasm of fibroblasts, endothelial cells, leiomyocytes in the media, and in fibrocytes of the adventitia of mesenchymal arterioles. The location of the p21 oncoprotein overexpression was mostly similar to that of c-erbB-2 with stronger staining in the cytoplasm of squamous epithelial cells and weaker staining in mesenchymal arteriolar walls. The overexpression of c-erbB-2 and p21 oncoproteins may be corresponding to the cancer transformation and poor healing of radiation-induced skin ulcers.

Humans↗
PubMed1995

Abnormal location of p16 protein and overexpression of p53 protein in human radiation-induced skin cancer.

To evaluate the role of p16 multiple tumor suppressor (MTS1) and p53 protein in human radiation-induced skin cancer, we examined the expression of p16 and p53 in eight cases using immunohistochemistry. An abnormal location of p16 expression in the cytoplasm was found in seven of eight cases, but the expression of p53 in nuclei was noted in only three of eight cases. These findings suggest that the inactivation of p16 might be related to its binding with another unknown oncoprotein in the cytoplasm and thus lead to carcinogenesis.

Carrier Proteins↗
PubMed1995

[Mutation of P53 gene in a highly metastatic human lung cancer cell line].

PG cell line, derived from a lung giant cell carcinoma, has the characteristics of rapid growth and high tumorigenicity. When transplanted to nude mice, spontanious metastasis to lung and lymphnode is high in frequency and stable. To understand the molecular basis of PG's biological behaviors, expression of tumor suppressor gene p53 was studied. It was found that expression of p53 protein was increased as demonstrated by immunohistochemical stainning. A change in polymorphsim in exon 7 of p53 gene was detected by nonisotopic PCR-SSCP, suggesting a change in base composition. Thermal cycling sequencing of both strands of exon 7 demonstrated a transversion of CGG to CTT at codon 248. Similar study with the same methods on Ki-ras oncogene was done, but no mutation was found. The relationship between p53 gene mutation and the metastatic potential of PG cells needs further exploration.

Animals↗
PubMed1995

Experimental study on antiatherosclerotic treatment by PGE2 combined with vitamin E and estradiol.

The effects of single dose of PGE2 combined with vitamin E and with estradiol on experimental atherosclerosis were studied by means of morphological, ultrastructural, autoradiographic and several functional techniques. The results showed that two combined treatment groups had more coordinative inhibition on aortic and coronary atherosclerotic lesions, as well as on platelet aggregation, smooth muscle cell proliferation and lipid peroxidation than that of single dose of PGE2. It was revealed that the coordinative mechanism might be closely related to the synergistic inhibitory function of above-mentioned drugs on endothelial permeability, platelet aggregation, smooth muscle cell proliferation and lipid peroxidation.

Animals↗
PubMed1995

YAG laser resection for the membrane on anterior surface of intraocular lenses.

The results and methods of YAG laser resection for the membrane forming postoperatively on the anterior surface of intraocular lens (IOL) in 33 eyes (31 cases) were reported. A monomode single pulse YAG laser was used to do a circular incision along the pupilar margin and blow it up. A multimode defocus burst was used to peel off the shrunk flap from the lens surface. The membrane in 27 eyes (81.8%) was completely removed in the first resection. The mean burst number was 49.2 +/- 26.3. The average energy of each burst was 1.3 mJ and the average total energy of each treatment was 62.1 +/- 37.1 mJ. Except 3 eyes with little blood oozing from iris near the pupilar margin, 4 eyes having foggy spots on IOL surface and 2 eyes with mild transient increased intraocular pressure (IOP) after resection, there were no other complications. The resection is safe and effective, could be instead of the second operation for unabsorbable organized membranes or the membrane causing blockage glaucoma, could accelerate the recovery of visual acuity and shorten or substitute medical treatment for thick membranes.

Adolescent↗
PubMed1995

[Detection of the apoptosis-suppressing oncoprotein bcl-2 in ameloblastomas].

The product of apoptosis-suppressing oncoprotein bcl-2 can block apoptosis and result in the development of tumors. In this study, the expression of bcl-2 was observed in 40 cases of ameloblastomas by immunohistochemical staining. The results showed that the epithelium and reduced enamel epithelium of the enamel organ, the odontoblasts, basal cells of odontogenic cysts, normal oral epithelium and 90% (36/40) of ameloblastomas were positive for bcl-2, indicating that the expression of bcl-2 in odontogenic epithelium may be related to the degree of differentiation and proliferation of cells, the overexpression of bcl-2 may be associated with the development of ameloblastoma.

Ameloblastoma↗